how to copy s3 object from one bucket to another using python boto3

Since you are using s3 service resource, why not use its own copy method all the way?

#!/usr/bin/env python
import boto3
s3 = boto3.resource('s3')
source= { 'Bucket' : 'bucketname1', 'Key': 'objectname'}
dest = s3.Bucket('Bucketname2')
dest.copy(source, 'backupfile')

You can try:

import boto3
s3 = boto3.resource('s3')
copy_source = {
      'Bucket': 'mybucket',
      'Key': 'mykey'
    }
bucket = s3.Bucket('otherbucket')
bucket.copy(copy_source, 'otherkey')

or

import boto3
s3 = boto3.resource('s3')
copy_source = {
    'Bucket': 'mybucket',
    'Key': 'mykey'
 }
s3.meta.client.copy(copy_source, 'otherbucket', 'otherkey')

Note the difference in the parameters